1. Field of the Invention
The present invention relates to a treatment container for corrosive-gas plasma etching or depositing such as chambers and bell jars for use in depositing apparatuses and etching apparatuses, and to a method for manufacturing such a treatment container.
2. Prior Art
Conventionally, there have been used, in the process of manufacturing semiconductor devices, a depositing apparatus for creating thin films on a semiconductor wafer through transformation of a reactant gas to plasma, and an etching apparatus for performing fine processing. Plasmic reactant gas has an advantage of enabling the wafer to be deposited or etched at relatively low temperature, without higher temperature required to the wafer.
FIG. 6 epitomizes a prior art treatment apparatus, i.e. a treatment container 1, having the shape of a hanging bell called a bell jar. In an etching apparatus, a workpiece W is placed on a stage 6 inside the treatment container 1 of silica glass into which a reactant gas and a corrosive halide gas are introduced. In the step of transforming the reactant gas to plasma, the workpiece W is etched to partially remove or smooth its surface (see Japanese Patent Laid-Open Publication No. 5-217946).
In the case of a depositing apparatus, a treating container takes the form of a chamber with ceramic fragments lined to the inside surface thereof. A semiconductor wafer to be treated is placed inside the chamber in which a material gas and a corrosive halide gas are introduced, and then through transformation of the reactant gas to plasma, a thin film is layered on the surface of the workpiece.
As shown in FIG. 6, a top portion of the treatment container 1 is integrally connected to an extended introduction tube 14 for introducing gas, and an induction coil 5 arranged outside the introduction tube 14. Inside the treatment container 1, there is provided a support member 6, or a stage, for supporting a workpiece W thereon. The induction coil 5 generates a high frequency electromagnetic field inside the introduction tube to convert a reactant gas supplied into the introduction tube 14 to plasma. The plasma is led to the inside of the treatment container 1 to involve in reaction on the surface of the workpiece.
As described above, the treatment container 1 uses ceramics or silica glass in the portion that is exposed to corrosive halide gas and/or plasma. The surface of the portion has been previously smoothened to avoid corroding the surface by plasma.
Such a reactant gas for the above treatment, however, is corrosive halide gas including fluorine or chlorine containing gases. The gas, if used alone as a gas or transformed to plasma, reacts with ceramics or silica glass constituting an inner surface 102 of the treatment container 1, creating and depositing halide compounds on the inner surface 102. When evaporated or broken by plasma, halide particles fall down from the surface and adhere onto the workpiece W. Such particles may adversely affect performance of electronic parts produced from the workpiece W.
Japanese Patent Laid-Open Publication No. 11-283972 discloses a treatment container in which numerous asperities are formed on the surface of the portion exposed to corrosive gas and/or plasma which is composed of a ceramic or silica glass to avoid contaminating the workpiece. However, the above proposed technique failed to accomplish efficient corrosive resistance of the container.
Halides created on the surface of the container often react with oxygen contained in a mixed gas which is introduced into the treatment container 1 to form oxide or oxynitride, which is apt to be attached to a lower temperature area in the surface of the treatment container 1. After being deposited in some quantity, the oxide or oxynitride is exfoliated from the container surface in the form of particles which are attached onto the surface of the workpiece W to be treated, such as a semiconductor wafer. As a result, such attached materials as a halide exerts negative influence on the performance of the workpiece W. Therefore, it is important to suspend the use of the apparatus and clean away halide composite from the inner surface 102 of the container 1.
There has been also a problem that ceramics excellent in corrosion resistance, which are not always sufficient in strength, cause breakage or cracks of the treatment container 1 while being handled.
An object of the present invention is to provide a treatment container capable of preventing halide and other reaction products from depositing on a workpiece during treating with corrosive gas plasma inside the treatment container, allowing the container to be used for long-term processing.
Another object of the present invention is to provide a treatment container with strength sufficient enough to prevent defects from generating while handling it for treating with corrosive gas plasma.
According to the present invention, the treatment container includes a portion of the treatment container which is exposed to corrosive halide gas and/or plasma is formed with a sintered body mainly including yttria and alumina, and is provided with a roughened surface having a mean roughness Ra of 1.5 to 10 xcexcm, according to the definitions of JIS B0601, on the inner surface thereof.
In the present invention, even though reaction products such as a halide are generated on said roughened surface in the treatment container due to reaction of a corrosive gas, particularly, halogen-containing gas, to the sintered material constituting the container, the roughened surface portion can prevent the reaction products from exfoliating as particles from the surface, prolong a period of time till the particles fall down, and therefore decrease contamination to the workpiece. This can decrease the frequency of periodic cleaning operations of the container, providing long operating period of time required for the depositing or etching apparatus.
Further, the present invention may include a method of manufacturing the treatment container which has a portion to be exposed to corrosive halide gas and/or plasma, wherein the portion is roughened to a mean roughness Ra of 1.5 to 10 xcexcm by blasting the inner surface, of the sintered body, of the container, thereby effectively roughening the portion of the inner surface.
In the present invention, there is another method for manufacturing a treatment container in which in molding a molded body using a rubber press from a material powder, a roughened surface configuration is preparatorily formed on the outer surface of a core for pressing the inner surface of the container, and, in the rubber-pressing step, the configuration on the core is transferred to the inner surface of the molded body, and thereafter the firing of the molded body is performed to form a sintered body having the inner surface roughened with the predetermined configuration.
In addition, the treatment container of the present invention may contain a resin film applied to the outer surface thereof. The resin film can reinforce a wall portion susceptible to generation of cracks by buffering mechanical impact, thereby enabling considerable decrease in breakage or cracks of the treatment container during being handled. A desirable resin film covering the surface of a ceramics can also provide the container with a high resistance to strongly corrosive chemical components used for removing and cleaning contaminants which has formed on the inner surface of the treatment container for long time use.